Pneumatic tire having sealant layer

ABSTRACT

A tire with a built-in puncture sealant comprising a supporting tire carcass comprised of one or more layers of ply, an outer circumferential tread, and a radially inner layer, a pair of beads, sidewalls extending radially inward from the axial outer edges of the tread portion to join the respective beads, a sealant comprising a butyl ionomer containing degradation product, disposed inwardly from said tire carcass inner layer, wherein said sealant provides self-sealing properties to the tire.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims the benefitof, U.S. patent application Ser. No. 14/572,138, filed Dec. 16, 2014,which is entitled “Pneumatic Tire Having Multiple Built-In SealantLayers and Preparation Thereof,” and is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention is directed to tires having inner sealant layers,and in particular to tires having a butyl ionomer containing sealantlayer formed from sealant precursor layer.

Tire puncture is an inherent issue for rubber pneumatic tires. Becauseof that, sealants have been developed and placed as a layer inner to thetire tread and plies to minimize the impact of the puncture. Further,punctures can occur at any temperature. A single layer of sealant of lowviscosity may work very well at low temperature, but at hightemperatures, it might achieve a very low viscosity, which would allowit to flow and pass out of tire during use. By depleting the tiresealant, the tire loses its puncture sealing capacity. Likewise, asingle layer of sealant of high viscosity may be very good for hightemperature but might be almost solid at cold temperature and thusunable to flow to plug puncture in tires at cold temperature.

Tires with built-in sealant layer are known in the art. Typically, thesetire sealants are formed during tire cure by thermal degradation ofperoxide-containing butyl-rubber-based sealant precursor layers, such asfor example, U.S. Pat. Nos. 4,895,610; 6,962,181; 7,073,550; 7,674,344;and 8,293.049; and U.S. Patent Publication Nos. 2005/0113502 and2005/021568, the teachings of which are all hereby incorporated byreference. Sealant layers may be of black or non-black colors and mayincorporate short fibers, such as polyester or polyurethane fibers, andother filler aggregate into sealant layers to help to plug nail holepunctures.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a tire with a built-in puncturesealant comprising a supporting tire carcass comprised of one or morelayers of ply, an outer circumferential tread, and a radially innerlayer, a pair of beads, sidewalls extending radially inward from theaxial outer edges of the tread portion to join the respective beads, asealant is formed during tire cure by thermal degradation of butylionomer containing precursor catalyzed by peroxide, disposed inwardlyfrom said tire carcass inner layer, to provide self-sealing propertiesto the tire.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the present inventionwill become apparent to those skilled in the art to which the presentinvention relates upon reading the following description with referenceto the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a tire using the present invention;and

FIG. 2 is a cross-sectional enlarged view of the tire in FIG. 1 takenalong line 2-2 in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a tire having a sealant layerformed from a precursor during tire cure by thermal degradation of butylionomer containing composition catalyzed by peroxide. Thus the tire hasa thermally degraded butyl ionomer sealant layer disposed inside thetire formed from a precursor layer. The tire comprises a supporting tirecarcass comprised of one or more layers of ply, an outer circumferentialtread, and a radially innermost innerliner layer, a pair of beads,sidewalls extending radially inward from the axial outer edges of thetread portion to join the respective beads, a sealant layer, and a coverlayer, disposed on said tire carcass innermost layer, wherein thesealant is formed during tire cure by thermal degradation of butylionomer based compound in the presence of peroxide to form an innerlayer of thermally degraded butyl ionomer sealant, disposed inwardlyfrom said tire carcass inner layer, to provides self-sealing propertiesto the tire.

As used herein, the term “sealant precursor” means the compound byitself is not a sealant, but it is transformed into sealant by thermaldegradation during the curing step of tire making. The “precursor layer”is the layer of sealant precursor. The precursor layer can be 100% butylionomer rubber or can be butyl ionomer rubber blended with other rubbersthat can be transformed into a sealant, such as a mixture or both butylionomer and butyl rubber, which also degrades during tire curing at hightemperature to form low molecular weight easy to flow tacky sealants. Asused herein, “degraded” or “degradation” means breaking of rubber chaingiving rise to lower molecular weight rubber.

In the present invention, a sealant precursor layer is assembled into anunvulcanized rubber tire (generally called a Green Tire) usingconventional tire building techniques. After an unvulcanized tire isbuilt, including such a sealant precursor layer, the tire is vulcanizedemploying standard methods. Such a sealant precursor layer is assembledinto the tire inwardly from the tire's supporting carcass and outwardlyfrom an inner liner layer (which can be an air barrier layer) in theunvulcanized tire. Alternatively, the sealant precursor layer can alsobe placed inner to tire inner liner, and, in this case a sealant coverlayer is needed, inner to sealant precursor layer with width greaterthan the sealant precursor layer. The purpose of the sealant cover layeris to prevent contamination of the tire curing bladder from lowmolecular weight tacky sealant formed from the precursor layer.

The physical nature of the sealant precursor layer is that its viscosityis high enough to permit easy handling during the standard steps in theconstruction of an unvulcanized tire and during the vulcanization(curing) operation: that is, the sealant precursor layer has enoughuncured strength (modulus) to retain its shape during building, enoughtack to stick to adjacent layers during building and enough strength toretain its shape during the application of the high pressure duringvulcanization.

As the tire is vulcanized with sealant precursor layer, sealant layer isformed in situ, by thermal degradation of butyl ionomer. In effect, thebutyl ionomer rubber in the polymer composition layer is degraded to alow viscosity, easy to flow tacky material, which has puncture sealingproperties. Thus, the sealant precursor layer is transformed into apuncture sealant layer during the high temperature curing of the tire.The degradation of the sealant precursor layer is effectuated by thepresence of one or more peroxides which acts as a catalyst.

Most rubber compositions, e.g. those based on natural rubber, butadienerubber, styrene butadiene rubber etc. when heated in the presence ofperoxides, harden due to cross linking reactions. However, butyl rubberbased compositions, when heated with peroxide, the material softenspredominantly due to thermal degradation (chain cessation). Brominationof butyl rubber produces bromobutyl rubber. Unlike butyl rubber,bromobutyl rubber crosslinks in the presence of peroxide thus givingrise to hardened rubber. Ionic butyl is produced by chemical reaction ofbromobutyl as shown below:

During experimentation, it was unexpectedly found that unlikebromobutyl, ionic butyl based compounds degrade in the presence ofperoxide to softer material. Thus compositions containing ionic butyland suitable peroxides were formulated as sealant precursors thatdegrade during high temperature tire cure and form easy to flow tiresealant material.

Butyl ionomers are derived from halobutyl rubber. Halobutyl rubbers arederived from butyl rubber. Butyl rubber is produced by copolymerizingisobutylene with small amounts of isoprene. Generally, butyl rubbercontains from about 0.5 to 4 mole % isoprene and from about 96 to 99.5mole % percent isobutylene unit. The butyl rubber that can be employedin the polymer composition of the tires of this invention has a numberaverage molecular weight in the range of 200,000 to 600,000 andpreferably in the range of about 300,000 to about 500,000, and a Mooneyviscosity (ML 1+8 at 125° C.) ranging from about 25 to 65. Butyl rubberis then converted to bromobutyl rubber, which is then transformed tobutyl ionomers by converting the bromine functionalities into ionicimidazolium bromide groups which results in the formation of reversibleionic associations that exhibit physical cross-linking ability.

At least one butyl ionomer is available commercially from Lanxess withtrade name X_Butyl™ I4565P that has ML(1+8) value of 56±4 MU at 125° C.and ion content of 0.4±1 mole %, total reactive bromine content of0.5±0.2 mole % and 1,4-isoprene content of 0.5±0.2 mole %.

Compositions based on 100 phr butyl ionomer rubber can be used in makingsealant precursor. Butyl ionomer can be used in combination with otherelastomers that degrade at tire cure temperature. One example of suchpolymer is butyl rubber. Thus, 100 to 5 phr ionic butyl in combinationwith 0 to 95 phr butyl rubber can be used to create tire puncturesealant composition.

It is preferable for the polymer composition layer assembled into thetires of this invention to have the following composition in parts perhundred rubber (phr):

100 phr butyl ionomer rubber e.g. X_butyl™ I4565P from Lanxess

about 10 to 100 phr of silicon dioxide e.g. Sidistrar 320 or otherfiller

about 1 to 15 phr of tackifier e.g. Wingtack 85 from Total

about 20 to 200 phr calcium carbonate e.g. Hubercarb Q3 from Huber

about 5 to 35 phr oil, and

from about 1 to 16 phr suitable peroxide.

Any peroxide or combination of peroxides that catalyze the degradation(chain cessation) of ionic butyl based precursor compound at tire curetemperature (approximately 150° C.) can be employed. Preferably peroxidecompounds are employed which only disintegrate at high temperatures,that is, above about 100° C. (212° F.). Examples of such peroxides aretert-butyl perbenzoate and dialkyl peroxides with the same or differentradicals, such as dialkylbenzene peroxides and alkyl peresters.Preferably the peroxide degradation catalyst employed will contain twoperoxide groups. Frequently the peroxide groups are attached to atertiary butyl ionomer group. The basic moiety on which the two peroxidegroups are suspended can be aliphatic, cycloaliphatic, or aromaticradicals. Some representative examples of such peroxide degradationcatalyst include: 2,5-bis(t-butyl peroxy)-2,5-dimethyl hexane;1,1-di-t-butyl peroxy-3,3,5-trimethyl cyclohexane; 2,5 -dimethyl-2,5-di(t-butyl peroxy)hexyne-3; p-chlorobenzyl peroxide;2,4-dichlorobenzyl peroxide; 2,2-bis-(t-butyl peroxy)-butane; di-t-butylperoxide; benzyl peroxide; 2,5-bis(t-butyl peroxy)-2,5-dimethyl hexane,dicumyl peroxide; and 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane. Suchperoxide degradation catalyst can be added to the polymer compositionlayer in pure form (100 percent active peroxide) or on an inert,free-flowing mineral carrier. Calcium carbonate and silica are someexamples of inert carrier. Such carrier composition containing fromabout 35 to 60 weight percent active ingredient (peroxide) can beemployed very successfully. For example, 40 percent by weight dicumylperoxide on an inert carrier can be employed as the peroxide degradationcatalyst in the polymer composition layer with good results.

While the mechanism may not be fully understood, it is within the scopeof the present invention to employ an activating agent, such as2,2,6,6-tetra alkyl piperidine based hindered amine, which will activatethe organoperoxide, and in a sense, enable a reduction in the amount ofthe organoperoxide to more efficiently degrade the butyl ionomer rubberduring the formation of the sealant layer. Such activating agents areknow in the art, such as U.S. Pat. No. 7,674,344 to D'Sidocky et al.,the disclosure of which is incorporated by reference.

One representative example of such 2,2,6,6-tetra alkyl piperidine basedhindered amine is, for example, a 50/50 mixture ofpoly[[6-1,1,3,3,-tetramethylbutyl)amino]-s-triazine-2,4-diyl][2,2,6,6,-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]] compound(referred to herein as “PTP”) and bis(hydrogenated tallow alkyl), aminesoxidized and sold as Irgastab® FS410 FF from BASF.

Another example of peroxide activating agent is a mixture of PTP,bis(hydrogenated tallow alkyl) amine oxidized, andbis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate sold as Irgastab® FS811from BASF.

Another example of peroxide activating agent ispoly[[6-[1,1,3,3,-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][2,2,6,6,-tetramethyl-4-piperidyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]available as Chimassorb® 944 FDL from BASF.

In practice, exemplary of composites which contain, and therefore arecomprised of, said PTP are composites comprised of said PTP which mayalso comprise said bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate andwhich may also optionally contain an oxidized bis(halogenated tallowalkyl amine). In practice, the aspect of utilizing said 2,2,6,6-tetraalkyl piperidine based hindered amines, and particularly said PTP orcomposites of 2,2,6,6-tetra alkyl piperidine based hindered amines whichcontain (include) said PTP to activate the organoperoxide in thedegradation of the butyl ionomer rubber of the sealant precursor isconsidered herein to be important in order to reduce as much as possiblethe concentration of the organoperoxide in the sealant precursor butylionomer rubber-based composition, as well as excess unreactedorganoperoxide which may remain in the resultant built-in sealant layerwhich may, in turn, gradually become available to contact rubbercomponents of the tire adjacent to the built-in sealant layer.

The various components of the sealant layer can be mixed together usingany convenient rubber mixing equipment, such as a Banbury mixer. Thisrubber composition used in the sealant layer has sufficient viscosityand unvulcanized adhesion to enable its incorporation into anunvulcanized tire without departing from standard, long standing tirebuilding techniques and without the use of complicated, expensive tirebuilding equipment.

The strip of butyl ionomer based sealant precursor composition shouldextend from one shoulder of the tire to the other, in other words, itshould cover the crown area of the tire. The thickness of the sealantprecursor layer can vary depending on tire size. Generally, thethickness of the polymer composition layer will range from about 0.1 cm(0.04 inches) to about 0.635 cm (0.25 inches). It is generally preferredfor the polymer composition layer to have a thickness of 0.2 cm (0.08inches) to 0.4 cm (0.16 inches). In passenger tires it is normally mostpreferred for the polymer composition layer to have a thickness of about0.25 cm (0.1 inches).

After the unvulcanized pneumatic rubber tires of this invention areassembled, they are vulcanized using a normal tire cure cycle. The tiresof this invention can be cured over a wide temperature range. However,it is generally preferred for the tires of this invention to be cured ata temperature ranging from about 132° C. (270° F.) to about 166° C.(330° F.). It is more preferred for the tires of this invention to becured at a temperature ranging from a 143° C. (290° F.) to 154° C. (310°F.). It is generally preferable for the cure cycle used to vulcanize thetires of this invention to have a duration of about 10 to 14 minuteswith a cure cycle of about 12 minutes being most preferred.

The present invention employs a standard tire-building process. Afterthe green (uncured) tire is built, an optional protective film can beapplied on the top of the innermost sealant cover layer. The width ofthe film is slightly wider than the sealant layer (approximately 2inches more on both sides). This film protects the tire curing bladderand keeps it clean in case the innermost sealant cover layer ruptures ortears in the mold. Such films are known in the art. One such film is 2mil undrawn nylon-6, 6 available as DARTEK® C917 from Coveris HighPerformance Packaging. About 1″ (inch) of the film is overlapped at theend so that, after tire cure, it functions as a pull tab to facilitateeasy removal. Such a system is described in U.S. Pat. No. 7,332,047 toMajumdar, Logan, and Lukich, and is hereby incorporated herein byreference. The protective film can also be applied as first layer intire building drum. For convenience, the two edges of the film arepreferentially coated with a pressure-sensitive adhesive (PSA)-coatedthermoformable film. Such a system is described in U.S. Pat. No.7,419,557 to Majumdar and Page, and is hereby incorporated herein byreference. Although the film is not critical, Dynamically VulcanizedAlloy (DVA) film is preferred in tire building drum over nylon-6,6 filmbecause DVA has significantly lower low strain modulus and hence canexpand using less force during the green tire building process. Such amaterial is described in U.S. Pat. No. 8,776,851 to Majumdar, and ishereby incorporated herein by reference. Other examples are U.S. Pat.Nos. 8,021,730 and 8,158,721, hereby incorporated herein by reference.An activating agent for organoperoxide can be added in the sealantcomposition for faster degradation. Such a method is described in U.S.Pat. No. 7,674, 344 to D'Sidocky et al., and is hereby incorporatedherein by reference.

The present invention incorporates an inner liner and a sealantprecursor layer. The inner liner comprises bromobutyl rubber, carbonblack, naphthenic oil, stearic acid, phenolic resin tackifier, mixtureof aromatic hydrocarbon resins (as found in STRUKTOL® 40 MS resin,manufactured by Struktol Company of America), MgO, ZnO, Sulfur,2,2′-dithiobis(benzothiazole) (commonly sold as MTBS). The sealantprecursors comprise butyl ionomer rubber, paraffinic oil, silica, clay,titanium dioxide, talc, color concentrate (such as AKROSPERSE® E2295Green manufactured by Akrochem Corporation, AKROSPERSE® E6615 Orangemanufactured by Akrochem Corporation), blend of fatty acid derivativesprocessing additives (such as STRUKTOL® HPS 11 processing additivemanufactured by Struktol Company of America), in the firstnon-productive (NP) mixing pass. Organic peroxide, such as n-butyl4,4-bis(t-butyl-peroxy)valerate (such as TRIGONOX® 17-40B-GRmanufactured by AkzoNobel) can be added in the final productive (PR)pass.

Preferably the tire of the present invention is prepared in thefollowing sequences:

-   -   1. A sealant cover layer having formulation shown in Table 1 is        mixed and calendered to a thickness of 1 mm, and a width equal        to the inner liner width or slightly wider than sealant        precursor layer.    -   2. A precursor for the sealant having formulation shown in Table        2 is mixed and calendered to a thickness of 3 mm thick, and a        width equal to the tread width less about 15 mm (i.e., tread        width minus 15 mm).    -   3. The sealant cover layer (#1 above) is applied to the        tire-building drum.    -   4. Next, the precursor for the sealant (#2 above) is applied to        the tire-building drum.    -   5. Next, the inner liner is applied in a tire-building drum as        in typical tire building process followed by the rest of the        layers employed in a normal tire build.

EXAMPLES

A butyl ionomer rubber-based sealant precursor composition is preparedby mixing the ingredients in an internal mixer. The ingredients aremixed in a first, non-productive, mixing stage without theorganoperoxide, followed by a second, productive, mixing stage in whichthe organoperoxide is added. The ingredients are illustrated in thefollowing Table 2. The ingredients are in parts per hundred rubber.

TABLE 1 Sealant cover layer Ingredient Parts per Hundred Rubber (phr)Bromobutyl rubber 100 Carbon black 55 Naphthenic Oil 6 Stearic Acid 1Phenolic resin tackifier 4 STRUKTOL ® 40 MS Resin 8 MgO 0.15 ZnO 2.0Sulfur 0.5 MBTS (2,2′-Dithiobis(benzothiazole)) 1.5

TABLE 2 Sealant precursor Example 1 (phr) Non-Productive (NP) ButylIonomer Rubber 100.00 Paraffinic oil 25.00 Silica 50.00 CalciumCarbonate 100.00 Tackifier 5.00 AKROSPERSE ® 626 Blue 2.00 STRUKTOL ®HPS 11 Processing 4.00 Additive TOTAL (NP) 286.00 n-butyl4,4-bis(t-butyl-peroxy)valerate 12.00 ODR 150° C./R25/30′/3°Arc InitialTorque (lbf.in) 15 Minimum Torque, ML (lbf · in) 4.49 Torque at 30′ (lbf· in) 4.49 Green Strength Tensile (psi) 124 % Elongation 1255 M100 (psi)46 M200 (psi) 52 M300 (psi) 55

The resulting composition could be processed and used as a sealantprecursor in a tire building process. Table 2 also shows OscillatingDisc Rheometer (ODR) data of example 1. Initial torque of the precursorcomposition before degradation is 15 lbf.in; after 30 minutes at 150° C.(simulates tire cure), thermal degradation of precursor to sealant isformed resulting in lowering of final torque to 4.49 lbf.in. This changeis predominantly due to chain breakage (degradation) catalyzed byorganic peroxide. If there had been predominantly cross linking, thenthe torque would have increased to higher value as found in bromobutylcompound. Tensile properties of uncured sheet of sealant precursor layercalled green strength are also shown in Table 2. In Table 2, M100, M200,M300 are respectively modulus at 100%, 200% and 300% strains.

Additional butyl ionomer rubber-based sealant precursor compositionswere prepared by mixing the ingredients in an internal mixer. Theingredients are mixed in a first, non-productive, mixing stage withoutthe organoperoxide followed by a second, productive, mixing stage inwhich the organoperoxide is added. The ingredients are illustrated inthe following Table 3. The ingredients are in parts per hundred rubber.

TABLE 3 ADDITIONAL EXAMPLES Example 2 Example 3 Example 4 Example 5Non-Productive (NP) Butyl Rubber (Butyl BK- 100 70 30 1675) Ionic Butyl14565P 30 70 100 Wingtack 86 tackifier 30 30 30 30 resin Hubercarb ® Q3calcium 100 100 100 100 carbonate Sidistar ® 320 silica 50 50 50 50Akrosperse ® 802 2 2 2 2 Yellow Struktol WB42 4 4 4 4 processingadditive Total (NP) 286 286 286 286 Productive 2^(nd) Pass NP 286 286286 286 Vul-Cup 40KE¹ 3 3 3 3 Di-Cup 40KE² 9 9 9 9 TOTAL 298 298 298 298ODR 302° F./3°Arc/50 Rotor/30 minutes Torque at 0 min 20 20 20 20 (lbf ·in) Torque at 30 min 1.33 1.55 2.49 3.36 (lbf · in) Green StrengthTensile (psi) 33 171 187 338 Elongation (%) >900 927 534 707 M100 (psi)316 541 542 699 M200 (psi) 269 661 693 938 M300 (psi) 211 818 905 1304notes: ¹Vul-Cup 40KE is 40% a,a′-bis(tert-butylperoxy)diisopropylbenzene²Di-Cup 40KE is 40% dicumyl peroxide

All of the compositions had initial torque of approximately 20 lbf.in,which reduce to less than 4 lbf.in due to thermal degradation in ODRequipment (30 minutes at 302° F.) thus forming sealant materials. Ionicbutyl containing materials (Examples 3, 4 and 5) have significantlyhigher green strength compared to 100% butyl rubber based composition(Example 2). Table 3 shows that tensile strength of 100 phr butyl-basedsealant is 33 psi (example 2) and it is jumped to 171 psi by justreplacing 20 phr butyl with 20 phr ionic butyl (example 3). Thus, it isanticipated that just a small amount of replacement of butyl with ionicbutyl (such as 5 phr) will significantly increase the tensile strength.Thus ionic butyl rubber containing sealant precursors, even if presentin small amount, will be relatively easier to handle compared to sealantbased on 100 phr butyl.

For ease of illustration, some internal materials of the tire have beenomitted from the drawings, such as belts and plies, but they remain inthe finished tire.

FIG. 1 illustrates the cross-sectional view of the cured tire 10 of thepresent invention, where the layers are not shown to scale since it isthe ordering of the layers, not the specific widths and thicknesses thatis important. The width can range from full tire width, down to a smallstrip along the center of the tire. FIG. 2 is a cross-sectional viewillustrating the layers shown in FIG. 1; as with FIG. 1, the layers arenot shown to scale since it is the ordering of the layers, not thespecific widths and thicknesses that is important. A sealant layer 102formed from its precursor during tire cure and a sealant cover layer orinner liner 104 are shown in a general form. Cover layer 104 is shownextending the width of the tire sidewalls 106, but it is employed as isknown in the art. Once the green tire is vulcanized, the sealant layer102 is formed from its precursor. FIG. 1 also illustrates the presentinvention in which the sealant layer is between inner liner 104 and alayer of squeegee 108. Squeegee layer 108 is between the innermost layerof supporting carcass 116 and the sealant layer 102, which is formedfrom precursor layer once the tire is cured. The use of a squeegee layeris known in the art and is optional and employed as needed in theprocess of creating the sealant layer. FIG. 1 also shows tread 114,supporting carcass 116, and the inextensible beads 118, which are partof the tire.

The cover layer has a 100% modulus of 0.5 MPa to 2.5 MPa. The sealantlayer is generated using a peroxide having a Self-AcceleratingDecomposition Temperature (SADT) in the range 50-140° C. The 100%modulus (M100) of sealant precursor is in the range 400-900 psi andpreferably in the range 450-700 psi.

The foregoing embodiments of the present invention have been presentedfor the purposes of illustration and description. These descriptions andembodiments are not intended to be exhaustive or to limit the inventionto the precise form disclosed, and obviously many modifications andvariations are possible in light of the above disclosure. Theembodiments were chosen and described in order to best explain theprinciple of the invention and its practical applications to therebyenable others skilled in the art to best utilize the invention in itsvarious embodiments and with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A tire with a built-in puncture sealantcomprising: a supporting tire carcass comprised of one or more layers ofply, an outer circumferential tread, and a radially inner layer, a pairof beads, sidewalls extending radially inward from the axial outer edgesof the tread portion to join the respective beads, a sealant comprisingthe degradation product of a butyl ionomer rubber sealant precursorcomposition disposed inwardly from said tire carcass inner layer, andwherein said sealant provides self-sealing properties to the tire. 2.The tire of claim 1, further including a cover layer over said sealant,wherein said cover layer is the innermost layer.
 3. The tire of claim 2,wherein said cover layer has a 100% modulus of 0.5 MPa to 2.5 MPa. 4.The tire of claim 1, wherein said butyl ionomer sealant precursorcomposition comprises, based on its polymer content, 100 parts by weightbutyl ionomer rubber composition comprising 20% to 100%, by weight, ofbutyl ionomer, said composition having a number average molecular weightof 200,000 to 500,000, and a Mooney viscosity ranging from about 40 to58, about 5 to 35 parts by weight of an oil extender, about 100 parts ofcalcium carbonate, about 50 parts of silica, and about 1 to 16 parts perhundred rubber (phr) of a peroxide degradation catalyst.
 5. The tire ofclaim 1 wherein said sealant layer is generated using a peroxide havinga Self-Accelerating Decomposition Temperature (SADT) in the range50-140° C.
 6. A method for making a tire comprising forming a greentire; adding a sealant precursor comprising a butyl ionomer compositioncomprising 5 to 100 parts per hundred rubber (phr) of butyl ionomer, andone or more peroxides to said green tire; curing said green tire;wherein said sealant precursor layer containing butyl ionomer degradesduring tire cure to form a sealant layer.
 7. The method of claim 6,wherein said polymer composition is disposed inwardly from saidsupporting carcass and outwardly from said inner liner wherein saidpolymer composition consists of based on its polymer content, 100 partsby weight butyl ionomer rubber composition having a number averagemolecular weight of 200,000 to 500,000, and a Mooney viscosity (ML 1+8at 125° C.) ranging from about 25 to 65, about 5 to 35 parts by weightof an oil extender, about 100 parts of calcium carbonate, about 50 partsof silica, and about 1 to 16 parts per hundred rubber (phr) of aperoxide degradation catalyst.
 8. The method of claim 6 wherein saidperoxide is selected from the group consisting of: butyl4,4-di(tert-butylperoxy)valerate; 2,5-bis(t-butyl peroxy)-2,5-dimethylhexane; 1,1-di-t-butyl peroxy-3,3,5-trimethyl cyclohexane;2,5-dimethyl-2,5di(t-butyl peroxy) hexyne-3; p-chlorobenzyl peroxide;2,4-dichlorobenzyl peroxide; 2,2, -bis(t-butyl peroxy)-butane;di-t-butyl peroxide, benzyl peroxide; dicumyl peroxide; and2,5-dimethyl-2,5di(t-butyl peroxy) hexane.
 9. The method of claim 6wherein said butyl ionomer rubber composition has a number averagemolecular weight of 300,000 to 400,000.
 10. The method of claim 6wherein said peroxide is a combination of dicumyl peroxide anddi(tert-butylperoxyisopropyl)benzene.
 11. The method of claim 6 whereinsaid rubber tire is shaped and cured at a temperature ranging from about132° C. (270° F.) to about 166° C. (330° F.).
 12. The method of claim 6wherein the sealant precursor composition further includes a peroxideactivating agent.
 13. Tire of claim 4 where 100% modulus (M100) ofsealant precursor is in the range 400-900 psi and preferably in therange 450-700 psi.
 14. The method of claim 12, wherein said peroxideactivating agent ispoly[[6-[1,1,3,3,-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][2,2,6,6,-tetramethyl-4-piperidyl)imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]].15. The method of claim 12, wherein said peroxide activating agent isone or more materials selected frompoly[[6-[1,1,3,3,-tetramethylbutyl)amino]-s-triazine-2,4-diyl][2,2,6,6,-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]] compound;bis(hydrogenated tallow alkyl) amines, oxidized;bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate.
 16. A tire producedusing the method of claim
 6. 17. A tire produced using the method ofclaim 12.